Computerized Prediction of In-canopy and Leaf Surface Microclimate for Greenhouse Vegetable Production

摘要

Microclimate at the leaf surface can have a significant impact on the epidemiology of fungal pathogens and the population dynamics of pests.Due to photosynthesis, transpiration and vapor condensation processes that occur on plants surfaces, leaf surface microclimate can be considerably different from climate of the surrounding air. These differences are especially significant in the greenhouse due to the limited air circulation and the use of heating and misting .Unfortunately, leaf surface climate conditions are not measured regularly in the greenhouse due to the imitations of measuring instruments and the non-uniform spatial distribution of microclimate variables in the greenhouse. The objective of this study was to develop a stand-alone computer simulator for predicting the in - canopy and leaf surface microclimate of greenhouse plants. This imulator (PSCLIMATE) uses parameters that describe the characteristics of the greenhouse structure and the plant canopy together with routine climate observations in the greenhouse as input to predict energy and mass transfer among air stratums and leaves. The output includes leaf temperature, surface vapor pressure deficit (VPD) and surface wetness duration (SWD). The model is also able to predict the profiles of solar radiation, air temperature and VPD from the botton to top of the canopy for any time period. The results of this study indicate that in-canopy microclimate can be predicted adequately and the temperature and VPD at shaded leaf surfaces can be predicted very well using above canopy climate observations if the characteristics of the greenhouse structure and plant canopy are specified.